Difference Between Chlorophyll and Chloroplast

Photosynthesis is the light driven reaction that converts carbon dioxide and water in to energy rich sugars. Photosynthesis is initiated by the capture of light energy by chlorophyll pigments. Chloroplast is the site where photosynthesis takes place.

Chloroplast

Chloroplast is a plastid type organelle. These are found in plant cells and other photosynthetic eukaryotes. Chloroplasts are somewhat similar to mitochondria. But the difference is that chloroplasts can be found only in plants and in protists. Chloroplasts contain chlorophylls, which gives a green colour appearance to the chloroplast. Endosymbiotic theory suggests that chloroplasts evolved from a prokaryote (bacteria). In addition to chlorophylls, chloroplasts also contain carotenoids. Chloroplasts normally contain 2 types of pigments. One type is chlorophyll, which includes chlorophyll a and chlorophyll b. carotenoids are of 2 types. Those are caroteine and xanthophyll. Chloroplasts are surrounded by a double membrane. A colourless region called stroma is located inside the chloroplast. Fluid filled membrane bound sacs called thylakoids run through the stroma. These are made up of disc shaped stacks called grana. These grana are interconnected to each other by lamellae. Thylakoids (lamellae and grana) contain photosynthetic pigments. Stroma contains enzymes, circular DNA, 70s ribosomes and photosynthetic products (sugar, starch grains and lipid droplets). Photosynthesis involves two reactions. They are the light reaction and the dark reaction. Light reaction takes place in thylakoids (grana and lamellae). Dark reaction takes place in the stroma.

Chlorophyll

Chlorophyll is a green pigment. It can be found in a variety of organisms including plants, algae and cyanobacteria. Chlorophyll is one of the most critical factors for photosynthesis. Chlorophyll absorbs light in the blue and red regions of the visible spectrum and reflect green colour back. Plants, algae and prokaryotes synthesize chlorophylls. There are many types of chlorophylls. Those include chlorophyll a, chlorophyll b, chlorophyll c and chlorophyll d. Chlorophyll a is the most abundant. Chlorophyll a exists in several forms having red absorption peak at slightly different wave lengths. P700 in photo system I and p680 in photo system II are two examples. Chlorophylls have a characteristic light absorption pattern (it absorbs mainly blue and red light and reflect green light). Chlorophyll molecule has a hydrophilic head and a hydrophobic tail. Hydrophilic head is projected to the outside of the thylakoid membrane. Hydrophobic tail is projected to the thylakoid membrane. Light catching part of the molecule often has alternating single and double bonds. (Electrons can freely migrate around the molecule). These bonds contain electrons that are capable of being moved to higher energy levels by absorbing light. The ring has the potential to provide energized electron to other molecules.